No one will trust us ever again.
If the American people were stupid enough to elect a president who abandoned our allies and supported our (their) enemies once, then it only makes sense to think that it could happen again.
Even if the incarnation of Ronald Reagan came back to the White House, and even if every president thereafter were a Reagan clone, our (former) allies will always be reluctant to believe we won’t leave them twisting in the wind.
I do believe you are right and it goes much further than just Presidencies. We have federal agencies completely out of control who would usurp a Reagan clone in half a heartbeat so what good would it do trusting a staunch Constitutional President of the United States?
The only way our allies swing back our direction is when a serious executive branch along with a serious legislative branch cleans house from top to bottom and starts disbanding many of the more recent federal agencies created in the last sixty years.